Epidermal homeostasis is disrupted in a host of human skin diseases, including psoriasis, chronic wounds, and cancer. Increased understanding of the gene regulatory control of epidermal growth and differentiation by epigenetic regulators, specifically histone arginine methyltransferase PRMT1 and histone arginine demethylase JMJD6, is the central focus of this training plan. First, we will define the role of the histone arginine demethylase JMJD6, which demethylates histone H4 Arginine 3 dimethylation (H4R3me2), in epidermal homeostasis. In our preliminary studies, we observed that the histone mark H4R3me2 is dynamically regulated during human keratinocyte differentiation. In cultured primary human keratinocytes, loss of the H4R3me2 histone arginine demethylase JMJD6 impairs calcium- induced differentiation. To extend these findings, we will define the role of JMJD6 in normal human epidermal tissue homeostasis at the level of intact tissue, leveraging the human tissue regeneration models established in our laboratory. We will also characterize the action of JMJD6 in epidermal growth and differentiation. Second, we will elucidate the role of the histone arginine methyltransferase PRMT1, which methylates histone H4R3, in early progression towards epidermal neoplasia. We recently observed that PRMT1 is required to suppress epidermal differentiation. Loss of PRMT1 by multiple validated short-hairpin RNAs (shRNAs) inhibits proliferation and induces differentiation marker gene expression. Furthermore, PRMT1 is overexpressed in multiple human cancer tissues. Since the first steps in tumor evolution is characterized by alterations in growth and differentiation, we hypothesize that PRMT1 is required for tissue progression toward neoplasia. We will therefore define the role of PRMT1 in epidermis undergoing neoplastic transformation. At the end of the proposed funding period, we hope to have characterized the mechanistic actions of both JMJD6 and PRMT1 gene regulatory proteins in the control of epidermal proliferation and differentiation as a foundation for the future development of new treatment strategies for human disorders of characterized by disrupted epidermal homeostasis.